1. Field of Invention
The present invention relates to screen seals for touch sensitive display devices and, more particularly, to seals for force-based touch sensor assemblies.
2. Related Art
The popularity of touch screens has increased significantly over the past several years. Many different technologies have been explored in an effort to produce a high-quality touch sensor that is reliable and cost effective. Examples of touch sensor technologies include capacitive, resistive, near field imaging (NFI), acoustical wave, infrared, and force. Common applications for touch sensors include computer monitors and mobile and handheld devices, such as personal digital assistants (PDAs).
Touch sensors typically possess features and qualities that are unique for a given technology. Each type of touch sensor technology presents specific challenges related to, for example, the recognition of a touch input, the determination of the position of a touch input to a touch sensitive structure of the sensor, reliability, size, weight, and cost. The requirements for force-based touch sensors present their own set of challenges for attaining a viable and reliable touch system. One feature that is particularly unique to some force-based touch technologies is the desirability for the touch surface to be movable relative to the frame and bezel of the device so that the displacement can be measured as indicative of the applied touch force. Known sealing methods and structures, when applied between the movable screen and the frame and bezel, introduce a sufficient amount of extraneous force input to the touch system that may adversely affect touch input measurements.
In order to create a seal, many touch sensitive applications use the device bezel to press firmly around the edges of a touch-equipped display screen or display overlay module. This arrangement provides a dust and/or liquid seal, and may also serve to stiffen and align the bezel. With force-based touch devices, it may be desirable that the bezel and/or frame of the device not rest directly against the display screen, since the variable handling forces transmitted to the screen when touching the bezel and/or frame can interfere with touch location accuracy.
Another challenge for many touch sensors relates to how they are mounted to a display device. It is common practice to retrofit existing display devices with a touch sensitive system rather than to create a unique display device design that addresses the specific needs of a touch sensitive sensor. It is also common for some manufactures of touch sensitive display devices, for example, display devices with resistive and capacitive touch systems, to use a precalibrated, self-contained touch system that can be dropped into an existing display device. Such self-contained touch systems provide some advantages such as increased ease in assembling the display device, and improved quality control because the self-contained touch system can be tested by the sensor manufacture prior to being mounted to the display device.